It is generally accepted by people who have a serious interest in food taste and texture that meat should not be heated above about 170.degree. F., at which temperature the meat is considered to be "well done". Many prefer heating to a much lower temperature on the order of, say 120.degree. F., or 140.degree. F. for "rare" or "medium" done meat. Higher temperatures cause protein foods to become dry and tough.
It is well known that by searing red meat over the coals of a hot anthracite furnace fire, a thin and tasty black char is produced on the surface of the meat while the interior remains rare, juicy and tender. Over such a hot fire, blackening on one side is achieved in about one minute, and such black-charred meat is judged by many to be noticeably superior to that of meat that is charred brown.
Barbecue grills yield two forms of energy, namely hot flue gases and radiant energy. Hot gases are inefficient for broiling because gases are poor conductors of heat. When a piece of meat, such as a steak, is placed above a fire in a conventional grill only a small fraction of the rising volume of hot gases contacts the meat surface. Most of the gases flow up and around the meat and their heat is lost to the atmosphere. Radiant energy emitted from the hot coals moves in straight lines, and most of the radiant energy rays which strike the meat surface are absorbed immediately and raise the temperature of the meat surface. With many prior art grills, flue gas temperatures are at about 1200.degree. F. At such temperatures the total heat output provided by the combination of hot flue gases and radiant energy generally is less than 40 watts per square inch at the grill surface. As a result of such low heat output, charring of meat at the grill surface takes on the order of four or more minutes per side. In the relatively long time required to char the meat at such relatively low temperatures and heat output, much of the meat interior is heated to over the well-done condition and increases in toughness. The interior of meat prepared on such prior art grills is usually well-done before its exterior is charred dark brown or black.